1. Field of the Invention
The present invention relates to a method of encoding and decoding in a wireless communication system, and more particularly, to a method and apparatus of encoding and decoding data using low density parity check (LDPC) code in a wireless communication system. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for simplifying complex operations and efficiently using the memory space.
2. Discussion of the Related Art
Generally, encoding signifies a process in which data is coded at a transmitting end to enable a receiving end to compensate for errors occurring from signal distortion and signal loss during data transmission through the air interface and recover the original data. Decoding is a process in which encoded data from the transmitting end is recovered to its original data at the receiving end.
A method of encoding using Low Density Parity Check (LDPC) code is known. The LDPC code is a type of error-correcting code invented by Robert Gallager in his PhD thesis in 1962. More specifically, the parity check matrix H, the elements of which are mostly comprised of ‘0’s, is a low density linear block code. The LDPC codes were largely forgotten when first introduced due to the high complexity computations, but were reinvented in 1995 and proven effective. Research of the LDPC codes is under way (Reference: Robert G. Gallager, “Low-Density Parity-Check Codes”, The MIT Press, Sep. 15, 1963. [2] D. J. C. Mackay, Good error-correcting codes based on very sparse matrices, IEEE Trans. Inform. Theory, IT-45, pp. 399-431(1999)).
The parity check matrix of the LPDC code has very few 1's in each row and column. As a result, even in a large block, decoding is possible through a repetitive decoding procedure and, if the size of the block becomes very large, the LPDC code nearly satisfies Shannon's channel capacity limit as in turbo coding.
The LPDC code can be defined by a (n−k)×n parity check matrix H, wherein ‘n’ denotes the size of codeword after encoding process and ‘k’ denotes the size of data bits before encoding process. The generator matrix G can be derived from the following equation.H×G=0  [Equation 1]
With respect to encoding and decoding using the LDPC code, the transmitting end uses the parity check matrix H and the generator matrix G to encode data according to Equation 2.c=G×u  [Equation 2]
In Equation 2, the symbol ‘c’ refers to codeword and ‘u’ refers to data frame.
Recently, a method of encoding data using only the parity check matrix H and not the generator matrix G is being used. With respect to the encoding method using the LDPC code, the parity check matrix H can be considered to be the most important factor. Because the size of the parity check matrix H is approximately 1000×2000 or larger in practical communication system, the process of encoding and decoding requires many calculations, complex expressions, and large storage space.
After the parity check matrix H is generated, the input source data is encoded using the generated parity check matrix H.